Area Forecast Discussion
Issued by NWS Aberdeen, SD

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FXUS63 KABR 231739 AAC
AFDABR

Area Forecast Discussion...UPDATED
National Weather Service Aberdeen SD
1239 PM CDT FRI SEP 23 2016

.UPDATE...
Issued at 1029 AM CDT FRI SEP 23 2016

Continue to see numerous showers and thunderstorms moving north-
northeast across the CWA. POP grids have this handled pretty well,
including timing the back edge of precip from south to north this
afternoon as the warm front pushes northward. Just made a few
minor adjustments based on current radar trends. Will also be
watching clearing line in the cloud cover moving northward
through the day as well, which has now moved into southern SD.
Current sky grids also seem to have a pretty good handle on this
so not many changes there. Web cams across the region also reveal
some fog, which has been dense at times in places. Will leave fog
mention in the grids through a good portion of the day as well.
Trickiest part of forecast today are the temperatures, which will
be challenging since it will all depend on where the clearing line
progresses today with the warm frontal push. Still expecting to
see 80s across the southern CWA by later this afternoon where sun
is expected to appear. Further north though, will likely be stuck
in the 60s with clouds hanging around much of the day.

&&

.SHORT TERM...(Today through Sunday Afternoon)
Issued at 334 AM CDT FRI SEP 23 2016

The early morning weather map showed a tight pressure gradient
overhead, with high pressure set up along the Manitoba/Ontario
border and low pressure organizing organizing across southwest WY to
CO. Plenty of low level moisture remains, some pockets of DZ and
visibilities dropping to around 2SM or less across portions of the
area, and especially over the higher terrain east near Summit.

Much of our weather will be dependent on the movement of the sfc
low to our southwest. Look for much warmer air and a line of
clearing to invade the southern third of the CWA late this
afternoon. The steady easterly winds will shift out of the
southeast across the entire area by 18Z, with the bulk of the
warmer air in the form of 850MB temps of 18-24C remaining across
the southern half of the state until closer to 00Z Saturday. The
sfc low is expected to shift northeastward, and stretch from
western SD to eastern CO by 00Z this evening, before focusing
across western ND from 12-18Z Saturday. Expect a strengthening low
level jet to form tonight with 925MB winds of 40-45kt. Despite
this, limited moisture in the dry slot will result in limited
shower/thunderstorm activity.

Expect thunderstorm chances to be on the increase Saturday as the
cold front swings in from central SD. Skinny MLCAPE values jump up
to near 750-1000J/kg from 15Z on east of ABR, with strong sheer. The
focus for strong to possible severe thunderstorms will hug the SD/MN
border through 21Z, before shifting into western MN. The marginal
SPC risk for Saturday afternoon looks reasonable for now, although
it may be upgraded later today. Will include the potential for
strong to severe storms in the HWO for Saturday afternoon east. The
sfc low will slowly exit across southern Manitoba Saturday night,
with breezy westerly and eventually northwesterly winds lingering
through the day Sunday. 850MB temps will fall to 3 to 7C Sunday as
wrap around moisture attempts to sneak across the northern counties
thanks to the 500MB low sliding across ND/Manitoba bringing a
sizable trough across the Plains States.

.LONG TERM...(Sunday Evening through Thursday)
Issued at 334 AM CDT FRI SEP 23 2016

Right now, there is good agreement in the gsm 00z solutions. The 00Z
gfs has come more in line with the ecmwf regarding departure of an
upper low track/timing on Monday and Monday night. Superblend pops
basically dry out during said timeframe. Beyond that, model trends
are all basically the same, building/drawing an upper level ridge
into the region for the middle to latter portions of the upcoming
week. The gfs, canadian and ecmwf solutions all separate some low
pressure energy out of the current western CONUS upper level
longwave trof and tuck it back across the far swrn CONUS through
Tuesday. Even though all three gsm deterministic solutions are
reloading another western CONUS trof this upcoming week, the gfs and
canadian are slower to lift this swrn conus energy out onto the
central/northern plains. The ecmwf lifts this energy out faster
while developing this western CONUS longwave trof, bringing small
precipitation chances to this cwa mainly Thursday/Thursday night,
while the gfs trend is similar, just slower, bringing small
precipitation chances to this cwa Friday/Friday night which is just
beyond the scope of the current 7-day forecast.

Temp-wise, not much change in the extended period superblend
guidance. Agree with the previous shift that even though this
upcoming week is not jam-packed full of anomalous cold low level
air, any night time periods between Monday and Thursday that contain
clear/mostly clear skies and generally light winds will have the
potential to experience low temperatures cooler than current
guidance, especially in the typical cool-spots and low lying areas.

&&

.AVIATION...(For the 18Z TAFS through 18Z Saturday Afternoon)
Issued at 1235 PM CDT FRI SEP 23 2016

Skies will gradually lift from current ifr/mvfr conditions this
afternoon and evening as a warm front pushes north. Thunderstorms
may still impact KMBG early this afternoon before exiting into ND.
As a cold front moves east on Saturday, mvfr cigs will fill back
in briefly in the morning.

&&

.ABR Watches/Warnings/Advisories...
SD...NONE.
MN...NONE.
&&

$$

UPDATE...TMT
SHORT TERM...KF
LONG TERM...Dorn
AVIATION...Wise



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